Accident Details
On April 4, 2019, at approximately 1215 eastern daylight time, a Cessna 175, registration N7622M, was substantially damaged during a forced landing near Edgefield, South Carolina. The pilot and a pilot-rated passenger were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Pre-Accident Events
The aircraft had not been flown for about six years before being purchased approximately one week before the accident. An individual who inspected the aircraft for purchase noted a stuck valve during examination of the engine and during an engine run. After purchase, the wings were removed, and the aircraft was transported to an airport for reassembly. The pilot, who was also an airframe and powerplant mechanic, reinstalled the wings and performed an annual inspection the day before the accident from memory without a checklist. During the inspection, the pilot noted low compression in the No. 2 cylinder, which he attributed to a stuck exhaust valve. No differential cylinder compression test was conducted. Corrective action consisted of staking the valve. Afterward, the engine was operated with no discrepancies noted, and the pilot flew the aircraft for about one hour during two separate flights with no reported issues.
According to the pilot, during the engine run-up check for the accident flight, the No. 2 cylinder exhaust valve stuck again. He secured the engine, staked the valve, and performed another engine run-up with no discrepancies. Before departure, he performed an engine run-up and noted each magneto drop was about 150 rpm. He also performed several full-throttle static engine runs, achieving a maximum rpm between 2,500 and 2,600. He then departed. After about 20 minutes of level flight, the engine began to run "a little shaky," similar to a stuck valve. The pilot turned toward a nearby airport, but the engine ran rougher and then lost power completely. He spotted a field and set up for a forced landing. During the landing roll, while maneuvering to avoid livestock, the left wing collided with a power pole.
Post-Accident Examination
Postaccident examination was performed by several Federal Aviation Administration (FAA) inspectors. An initial inspection revealed no contaminants in either fuel tank or fuel strainer; the aircraft had about 25 gallons of fuel on board. The carburetor bowl contained an unquantified amount of fuel, and the fuel strainer was full of uncontaminated fuel. There was no blockage from either tank through the fuel selector to the engine on any position of the fuel selector valve. The air induction and exhaust systems were free of obstructions. Two ignition leads for the right magneto were noted to be swapped. The engine was started and operated to only 1,500 rpm due to safety concerns.
During engine operation, there was a "noticeable skip coming from the engine." A check of the magnetos at low rpm revealed the engine "backfired and sputtered bad before shutting down" when the left magneto was selected, but the engine continued to run when the right magneto was selected. Inspectors did not have tools to determine magneto-to-engine timing or internal timing of the left magneto, which was removed and examined. It was disassembled completely in the field except for removing the coil and contactor, and internally appeared to be in good condition. No further examinations of the left magneto were conducted, and the reason the engine lost power when it was selected was not determined.
The pilot later stated that following recovery of the aircraft, he examined the engine and found the exhaust valve guide of one cylinder came out of the cylinder and attached to the valve. He also indicated that, on another cylinder, he found the pushrod socket out of position. The pilot did not respond to requests to clarify which two cylinders were affected.
According to Continental Aerospace Technologies Standard Practices Manual, cylinder removal and inspection is specified if one or more of the valves in the valve train are sticking.